For returning from a Web API 2 controller, I can return content with the response if the response is OK (status 200) like this:
public IHttpActionResult
I would recommend reading this post. There are tons of ways to use existing HttpResponse as suggested, but if you want to take advantage of Web Api 2, then look at using some of the built-in IHttpActionResult options such as
return Ok()
or
return NotFound()
Choose the right return type for Web Api Controllers